Shuttle carriers, straddle carriers, sprinter carriers, runner carriers and transporting carriers are used in ports for moving containers between port cranes and a storage area.
Those container carriers move freely while carrying the container in the cargo area; thus, they need to be able to move flexibly also in areas of little space. Carriers can move in a rotational movement around a rotation axis or in a skew movement in a diagonal or straight direction.
The turning of the carriers can he challenging. Carriers often have to drive a U-shaped path to be able to turn a container for 180 degrees. A problem of conventional container handling vehicles is thus the difficulty of maneuvering in tight places and achieving exactly the desired position and orientation. It is important to position a container in the right way, amongst others to ensure the accessibility of the door at the end of the container.
To solve the problem of turning of containers in tight places, a method of turning a carrier such as a straddle carrier or transporting carrier around its own center point has been introduced. This method, a so-called carousel maneuver, has been introduced. With the method, the container can be turned at a desired angle. One idea of the method is to turn the front wheels and the rear wheels at an angle enabling a turn around the center axis of the vehicle. In order to rotate counterclockwise about the center axis of the carrier, the driving direction of the left side front and rear wheels is reversed while the right side front and rear wheels remain going forward. For clockwise rotation, consequently, the left side front and rear wheels spin forward while the motion of the right side front and rear wheels is reversed. The carousel maneuver is for example mentioned in US20110108347.
There are, however, some challenges in the implementation of turning a container carrier's wheels to begin a turning or skew movement. A loaded container can weigh between 20 and 40 tons. This puts an enormous stress on the turning mechanism of the wheels of the carrier and makes the turning of the wheels more difficult. A great force is needed to turn the wheels while the carrier is carrying the container. Turning the wheels while the container is being carried also increases wear of the tires resulting in the frequent need to change the tires. Additionally, carrier's wheels are often turned on the same spot of the cargo area, resulting in wear of the ground surface on the spot.
The aim of this invention is to facilitate the process of maneuvering a container carrier, thus resulting in less wear of the carrier's components and the ground surface.